Dishwashing machine with liquid filtering cyclone



Apa'il 11, 1967 R. J. GILSON 3,313,311

DISHWASHING MACHINE WITH LIQUID FILTERING CYCLONE Filed Dec. 18, 1964 4 Sheets-Sheet 1 8 F L f L R L LI 1 e I I r 9 4 I +/& I i

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R. J. GILSON DISHWASHIN G MACHINE WITH LIQUID FILTERING CYCLONE Filed Dec. 18, 1964 4 Sheets-Sheet 5 April 11, 1967 R. J. GILSON 3,313,311

DISHWASHING MACHINE WITH LIQUID FILTERING CYCLONE Filed Dec. 18,1964 4 Sheets-Sheet 4 United States Patent 3,313,311 DISHWASHING MACHINE WITH LIQUID FILTERING CYCLQNE Robert John Giison, High Wycombe, England, assignor to Charles Colston Limited, High Wycombe, England, a corporation of England Filed Dec. 18, 1964, Ser. No. 419,355 Claims priority, application Great Britain, Dec. 23, 1964, 432/64 8 Claims. ((31. 1341t 9) This invention relates to liquid filtering systems for washing machines, and is particularly applicable to dishwashing machines. It can, however, be used for any type of washing machine in which a washing liquid becomes contaminated with particulate soil or debris removed from the articles being washed.

It is customary in domestic dishwashing machines for the washing liquid to be passed through a mesh type strainer before being recirculated through the spray device in the washing chamber. In practice it has been found undesirable to use a strainer having apertures less than about %32" to A in size due to the tendency for smaller apertures to become clogged with soil particles.

It is well known that there is a tendency for fine soil particles, which can pass through the strainer mesh, to deposit on and adhere to surfaces of articles in the machine which are not directly exposed to the full force of the washing spray, causing a gritty feel on such surfaces when dry. This effect, which is commonly known as redeposit, is one of the more prevalent causes of imperfect results from a domestic dishwasher. In many modern machines this tendency for redeposit to occur is only kept within acceptable limits by the use of multiple washes and rinses, often in combination with a prerinse; even so, objectionable redeposit can still occur with a heavily soiled load unless the user takes the trouble to scrape the bulk of the soil off the dishes before loading them into the machine.

A known means by which an improvement can be obtained is the use of a by-pass filter utilizing mesh of finer size than is practicable in a full-flow filter; in this way soil particles as fine as .005" to .01" can be filtered out, bringing about a substantial reduction of redeposit. Such a system is described in the specification of British Letters Patent No. 894,310. HOWBV8I,Wl1llSt giving good results, if this system is to operate efficiently it is essential for the user to clean the fine mesh filter at frequent intervals, and failure to do so can lead to an indifferent result.

According to the present invention, in a washing machine having a washing chamber through or within which, when in operation, washing liquid is caused continuously to circulate and to be sprayed upon articles in the washing chamber, a proportion of the liquid in circulation is subjected to a centrifuging action to separate it into relatively soil-free and soil-rich fractions, the soil-free fraction being returned to the washing chamber and the soil-rich fraction being isolated for discharge to the drain line during or on completion of a washing operation. Preferably, the relatively soil free liquid is sprayed upon surfaces of articles being washed in the chamber which are not directly exposed to the aforementioned and main spray.

Separation of the soil'free and soil-rich fractions is preferably obtained by passing the liquid through a cyclone or like centrifugally separating device connected to the liquid circulating system. In practice the cyclone may have its inlet connected to the pressure side of the circulating system.

Preferably a flow-restrictor element or valve is incorporated in the soil-rich discharge line from the cyclone in order to restrict the total amount of liquid discharged to the drain line during each washing period.

The soil-rich liquid may be collected in a settling tank 3,313,311 Patented Apr. 11, 1967 from which it is released intermittently into the drain line of the washing machine. Also the settling tank may be allowed to continually overflow, and the overflow may be returned to the washing chamber or to the cyclone.

According to the invention also a washing machine comprises the combination of a washing chamber having a spray device or impeller, by which articles placed therein are subjected to a liquid spray or flow, a cyclone or like centrifugal separating device through which part of the washing liquid is caused to flow, whereby the said liquid is separated into relatively soil-rich and soil-free fractions, and means for isolating the soil-rich fraction from the washing chamber, the soil-free fraction being returned to the washing chamber. The means for isolating the soil-rich fraction may comprise a settling tank into which the soil-rich output from the cyclone discharges, the tank being provided with an outlet which normally remains closed in order to limit the soil-rich discharge from the cyclone.

Conveniently, the settling tank has a pressure-responsive self-opening discharge valve, which valve is subjected to the pressure in the liquid circulating system so that on circulation of the liquid the valve will automatically close and conversely will automatically open to release the contents of the tank when circulation stops. The settling tank may also be allowed to overflow continually back into the washing chamber or into the cyclone.

The invention is illustrated in the accompanying drawings as applied to a d-ishwashing machine, in which:

FIGURE 1 is a sectional view of a dishwasher having a filtration system in accordance with the invention.

FIGURE 2 is a detail section on an enlarged scale of one type of settling tank.

FIGURE 3 is a view of the rear of a dishwasher, showing a modified arrangement.

FIGURE 4 is a longitudinal cross sectional view of the cyclone used in the dishwashers of FIGURES 1 and 3.

FIGURE 5 is another cross sectional view of the cyclone on the line A-A shown in FIGURE 4.

FIGURE 6 is a vertical cross section of the settling tank for use in the modified arrangement of FIGURE 3.

FIGURES 7 and 8 show two sections in perpendicular planes of a flow restrictor valve for use in the arrangement of FIGURE 3.

Referring to FIGURE 1 of the drawing, C indicates a washing chamber provided with racks R for holding the articles to be washed, access to the chamber and racks being through a door D. Circulation of the Washing liquid is by means of a pump P which draws liquid from a sump S in the base of the washing chamber and delivers a major part of the liquid through duct M to a spray member T from which it issues in the form of a main spray directed over the articles in the racks. A removable filter screen F of mesh sufficiently coarse to avoid any tendency to clog, may be located in the mouth of the sump.

In the system of this invention a liquid cyclone 7, has its tangential inlet 8 connected by a pipe 9 to the discharge duct M of the pump P.

The cyclone 7 (FIGURES 4 and 5) comprises an elongated conical body portion 40 tapering to an underflow outlet 12, the cone merging at its open end with one end of a cylindrical chamber 41 provided in its circumferential wall with a semivolute entry recess 42 through which the liquid passes from the inlet 8 into the cyclone. The other end of the cylindrical chamber is provided with a closure member 43 through which passes the overflow outlet or vortex finding tube 10 of the cyclone, the entrance 44 to the overflow lying on the axis of the cyclone at the open end of the cone.

A minor part of the liquid discharged by the pump enters the cyclone and is given a rotary movement by the tangential arrangement of the inlet 8 and by the semivolute curve of the entry recess 42, and soil particles in the liquid, if of greater density than the latter are thus subjected to a resultant centrifugal force tending to move them towards the Walls of the cyclone along which they pass with a spiral motion towards the outlet 12. The relatively soil-free liquid left towards the axis of the cyclone is discharged through the vortex finding overflow tube 10.

The overflow 10 of the cyclone is connected by a pipe 11 to discharge into the chamber C, and the underflow 12 discharges into a container 13, hereinafter called the settling tank. This settling tank has connected to its outlet 14, a short length of rubber tubing 15, which is surrounded by and sealed into a jacket 16, connected by tube 17 to the discharge line of pump P.

The other end of valve tube 15 is connected by a tube 18 to the drain line of the machine.

Operation of the system is as follows:

The washing liquid is continually re-circulated by pump P, and a proportion of the total circulatory flow (conveniently in the region of to 15%) is by-passed through line 9 to cyclone 7, from which most of said bypassed liquid is discharged through the cyclone overflow back into the washing chamber, to re-combine with the main circulatory flow.

As is well known in cyclone technology, the centrifugal forces acting on the liquid passing through the cyclone, cause any solid particles having a specific gravity greater than that of the liquid to move towards the apex of the cone and to discharge from the underflow, whilst conversely the liquid discharged from the overflow is relatively free from such particles, i.e., it is returned as relatively soil-free liquid to the washing chamber. By returning it direct to the washing chamber at a position in the upper part of the chamber as in the embodiment illustrated, it may be used to wash surface of articles not directly exposed to the main liquid spray.

The soil-rich liquid discharged from the underflow falls into the settling tank, eing restrained therein by virtue of the pump pressure in jacket 16, which causes the separator discharge valve tube to collapse (as shown in FIGURE 1) and close the outlet from the settling tank.

As the liquid level in the settling tank builds up, the pressure developed in the entrapped air acts to retard the ingress of further liquid from the cyclone underflow. In practice it is found that the underflow discharge falls in freely for a second or two, until the settling tank is roughly 10% filled. The underflow discharge then commences to slow down considerably, and eventually becomes so slow that it takes several minutes for the settling tank to fill with the result that, by the time the settling tank is completely full, the great bulk of the soil has been removed from circulation.

When the washing operation is completed and the liquid circulating in the machine has been drained away, the pumping pressure falls to zero: consequently the rubber valve tube 15, being freed from external pressure, will respond to discontinuance of the pump discharge pressure and will expand and on opening out, allows the relatively soil rich fraction isolated in the settling tank to fall into the drain line and be discharged together with the bulk of the liquid drained from the machine.

It will be understood that the valve tube 15, closed by pumping pressure, is shown by way of example only, and any other type of valve may be utilized to provide the same general effect, i.e., to close the settling tank outlet while the washing liquid is being circulated, and open it when the washing liquid is drained away. In such an alternative construction (not illustrated) the tube 15 passes between an anvil member and a plunger urged towards the anvil member by a piston or diaphragm exposed to liquid from the discharge line of pump P, the plunger being spring biased to move away from the anvil when the liquid pressure in the discharge line falls to Zero as the pump stops. As a further alternative, the settling tank outlet could be left open during the early part of the washing cycle in order to ensure a maximum rate of filtration, and be closed in the latter part of the washing cycle to reduce loss of liquid.

In a further variation, the liquid collected in the settling tank may be allowed to overflow back into the Washing chamber, and if desired a fine-mesh filter screen may be inserted in the overflow path to ensure that none of the soil particles collected in the settling tank are entrained in said overflow return.

For this purpose, as shown in FIGURE 2, a bottle 21, attached to the lower part of a liquid cyclone 22, has a fine-mesh filter screen 23, which screen acts as a partition to divide the bottle into two parts. The lower part has an outlet 24 connected to the drain line of the machine via a suitable discharge valve, indicated diagrammatically at 26, and the upper part has an outlet 25 communicating with the washing chamber.

In operation, soil-rich liquid discharged from the cyclone underflow collects in the lower part of bottle 21, being retained therein by the valve 26 in outlet 24. Liquid trapped in the lower part of the bottle can pass upwardly through filter screen 23 and out of top outlet passage means 25 into the washing chamber. At the end of the washing period, outlet valve 26 is opened, thus allowing the contents of bottle 21 to drain away. During this draining process, the filtered liquid in the upper part of bottle 21 will flow back through filter 23, i.e., in the reverse direction, thus flushing away any particles of soil that may have tended to adhere to the underside of the filter screen during the washing operation.

FIG. 3 shows a further modification. The cyclone 7 has its tangential inlet 8 connected by a by-pass pipe 9 leading out of the return flow duct M which delivers washing liquid from pump P to the spray member (not shown), all as previously described. The cyclone overflow 10' is connected by pipe 11 to discharge into the washing chamber, and may conveniently be arranged to discharge the liquid against those surfaces of the dishes which are not directly exposed to the main spray. The cyclone underflow 12' is connected to discharge into a settling tank 13 (FIG. 6), through an inverted diffusing cone 30, which delivers the soil-rich liquid to the lower part of the settling tank. The cone continuously increases in cross section towards it open lower end 31 to ensure that the velocity of the incoming liquid is gradually reduced so as to encourage the soil to settle gently without turbulence or eddying, whilst the discharge of the soil-rich liquid into the lower part of the tank avoids contamination of the relatively soil-free liquid in the upper part of the tank 13'. A vent 32 permit the escape of any air trapped in the cone into the upper part of the tank.

The settling tank, which is in the form of a cylindrical tube, having end portions 33, 34 provided with top and bottom outlets 28', 14, has its axis inclined to the vertical to further assist in suppressing unwanted internal circulatron of soil-rich liquid. The diffusing cone 30 is supported axially in the settling tank by radially extending ribs 35, an inlet 36 passing from the top of the cone through the vlvza ll of the tank being connected to the cyclone underflow The lower outlet 14 of the settling tank is connected by pipe 15 to a drain valve 27 (FIG. 3), and thence by pipe 18' to the drain line of the machine. The overflow passage or outlet 28 at the top of the settling tank 13' is connected to discharge into the washing chamber through a flow restrictor 28 (FIG. 3). Referring to FIGS. 7 and 8, this flow restrictor comprises a cylindrical chamber 5%, closed at one end by a cap 51, a tangential inlet passage 52 from the settling tank and an axial discharge or outlet passage 53 to the interior of the washing chamber. In use, the mass of rotating liquid set up in the chamber by the tangential position of the passage 52 produces a centrifugal head which acts as a back pressure in the inlet passage thus reducing the rate of flow in this passage. This arrangement is preferable to restricting the bore of the top outlet pipe from the settling tank as such a restricted bore is liable to become blocked as a result of furring in the pipe. In operation, the soil in the soil-rich discharge from the cyclone underflow 12 settles by gravity in the lower end of the settling tank 13", from whence it is discharged to the machine drain line Via the separate discharge or drain valve 27 which is synchronised to operate in unison with the machine drain. The relatively soil-free liquid in the upper part of the settling tank overflows through flow restrictor 28 into the washing chamber where it re-combines with the main circulatory flow. The characteristics of flow restrictor 28 are made such that the rate of flow is suflicient to allow the cyclone to operate efiiciently throughout the whole washing time,

without being so high as to interfere with free settling of soil in the settling tank; in practice it is found that the flow through 28 can conveniently be of the order of 5% of the flow through feed pipe 9'.

It is not, of course, essential that the cyclone should have the specific conical shape and configuration of the orthodox liquid cyclone, and any like form of liquid-operated centrifuging vortex chamber capable of separating the feed thereto into soil-rich and soil-free fractions, may be used. If desired, two or more cyclones could be used in series, i.e., the underflow of the first one discharged into the inlet of the next one, in order more heavily to concentrate the proportion of soil in the last underflow discharge.

By arranging for the soil-free liquid discharged from the cyclone overflow to flow back into the washing chamber, there is the further advantage, as indicated above, that by directing it to fall or spray over those surfaces of the soiled articles which are not directly exposed to the main washing spray, it will still further reduce redeposit by increasing the volume of liquid (and simultaneously reducing the amount of soil) reaching these relatively blind or shielded surfaces.

The filtering system of this invention has the advantage over existing systems that there is virtually no limit to the smallness of particle size dealth with, and no need for cleaning or other attention by the user. Moreover, the efficiency of the system as applied to a dishwasher is such as to eliminate the occurrence of redeposit without requiring the user to pre-scrape the dishes and without needing an undue multiplicity of washes and rinses.

What is claimed is:

51. A dishwashing machine comprising means providing a washing chamber; main spray means in said chamber; a pump; means for delivering liquid from said chamber to the inlet of said pump; a cyclone separator having an in let, a vortex finding tube and a discharge passage; a settling tank; means for delivering a major part of the liquid discharged by said pump under pressure to said main spray means; means for delivering a minor part of the 6 liquid discharged by said pump to said cyclone separator inlet; means for delivering relatively soil free liquid from said vortex finding tube to a secondary spray means in the upper part of said chamber where it will be available for discharge over dishes therein; and means for delivering the relatively soil rich fraction of said liquid from the discharge passage of said separator to said settling tank.

2. A dishwashing machine according to claim 1 including a discharge valve for controlling the removal of soil from said settling tank, said valve being openable when washing liquid is drained from said washing chamber.

3. A dishwashing machine according to claim 2 in which said valve is closed in response to pump discharge pressure and is responsive to discontinuance of pump discharge pressure for opening.

4. A dishwashing machine according to claim 1 in which said means for delivering relatively soil free liquid from said vortex finding tube to said chamber includes said secondary spray means positioned to spray said relatively soil free liquid over those surfaces of articles being Washed in said chamber which are not directly exposed to the spray from said spray means.

5. A dishwashing machine according to claim 1 including overflow passage means for conducting liquid from said settling tank above the bottom thereof to said washin g chamber.

6. A dishwashing machine according to claim 1 in which said means for delivering the relatively soil rich fraction of liquid from said separator to said settling tank includes a conical diffuser within said settling tank and means for delivering relatively soil rich liquid to the interior of said dilfuser, the lower, wider end of said diffuser being open to the inside of said settling tank.

7. A dishwashing machine according to claim 6 in which said settling tank is inclined to the vertical.

8. A dishwashing machine according to claim 1 including overflow passage means for conducting liquid from said settling tank above the bottom thereof to said washing chamber; and a flow restrictor in said overflow passage means, said flow restrictor having a cylindrical chamber, an inlet passage opening tangentially into said cylindrical chamber, and an outlet passage opening axially outwardly from said chamber.

References Cited by the Examiner UNITED STATES PATENTS 747,980 12/1903 Kennedy 134--109 X 1,706,938 3/1929 Roberts 134-109 X 2,352,356 6/1944 Albertson. 2,578,040 12/ 1951 Booth et al. 3,003,346 10/1961 Morris et al. 68-12 3,003,347 10/1961 Morris et a1 68--12 3,122,148 2/1964 Alabaster 134-56 3,129,711 4/1964 Schmitt-Matzen 13456 CHARLES A. WILLMUTH, Primary Examiner.

R. L, BLEUTGE, Assistant Examiner. 

1. A DISHWASHING MACHINE COMPRISING MEANS PROVIDING A WASHING CHAMBER; MAIN SPRAY MEANS IN SAID CHAMBER; A PUMP; MEANS FOR DELIVERING LIQUID FROM SAID CHAMBER TO THE INLET OF SAID PUMP; A CYCLONE SEPARATOR HAVING AN INLET, A VORTEX FINDING TUBE AND A DISCHARGE PASSAGE; A SETTLING TANK; MEANS FOR DELIVERING A MAJOR PART OF THE LIQUID DISCHARGED BY SAID PUMP UNDER PRESSURE TO SAID MAIN SPRAY MEANS; MEANS FOR DELIVERING A MINOR PART OF THE LIQUID DISCHARGED BY SAID PUMP TO SAID CYCLONE SEPARATOR INLET; MEANS FOR DELIVERING RELATIVELY SOIL FREE LIQUID FROM SAID VORTEX FINDING TUBE TO A SECONDARY SPARY MEANS IN THE UPPER PART OF SAID CHAMBER WHERE IT WILL BE AVAILABLE FOR DISCHARGE OVER DISHES THEREIN; AND MEANS FOR DELIVERING THE RELATIVELY SOIL RICH FRACTION OF SAID LIQUID FROM THE DISCHARGE PASSAGE OF SAID SEPARATOR TO SAID SETTLING TANK. 